1. Field of the Invention
The present invention generally relates to a stage device, and more particularly to a stage device which is moved with high accuracy in a X-Y direction and a rotating direction by using a planar motor.
2. Description of the Related Art
Concerning ultra-precision machining devices and semiconductor devices which are the basis of information processing technology, the demand for high-accuracy positioning and high-speed processing of stage devices, used for these devices, is increasing. For example, for the stage device which is a key component of a semiconductor exposure device, the positioning accuracy on the order of 10 nm and the movement range of several hundreds of millimeter are needed. And, in order to aim at improvement in the productivity of semiconductor devices, it is necessary to move the stage on which a work piece is mounted to the processing position at a high speed. For this reason, it is desirable to implement the stage device which solves all of the above-mentioned problems.
For example, in various semiconductor manufacturing devices used in semiconductor manufacturing processes, the stage device is provided so that the wafer used as a movable body is carried on the stage device and the wafer carried on the stage device is moved therein. The stage device includes a drive unit which drives the movement of the stage on which the wafer is carried to the base, and a position measuring device which measures the position of the stage to the base.
A stack type stage device is known as a conventional drive unit, in which the stage which is moved in the X direction only and the stage which is moved in the Y direction only are accumulated. Since it is necessary for the stack type stage device to have a high-horizontal rigidity, and there is a problem that the weight of the device itself becomes heavy and a large error of the position in the perpendicular direction may occur due to the influence of the weight.
A SAWYER motor is known as a drive unit which is devised in order to solve the above problem. The SAWYER motor is one of planar motors, and can move freely the stage in the X-Y direction and in the rotating direction.
The planar motor in the present specification is meant such that the structural part of the motor is provided in the stage, and, in association with the convex part provided in the base, the planar motor is able to lift the stage over the base and able to move the stage to a desired position directly, without using the X-direction and Y-direction shafts. For example, refer to Japanese Laid-Open Patent Application No. 05-328702.
Next, the stage device which uses the SAWYER motor will be explained with reference to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram of the stage device which uses the SAWYER motor, and FIG. 2 is a plan view of the structure of the stage device corresponding to the area A indicated in FIG. 1.
The stage device 200 generally includes a base 211, a pair of X-direction actuators 213, a pair of Y-direction actuators 214, a tilt actuator 216, a movable stage part 217, a fixed stage part 219, a chuck 221, a mirror 222, and a laser measuring instrument 223. The planar motor is constituted by the pair of X-direction actuators 213, and the pair of Y-direction actuators 214.
A plurality of convex parts 212 are provided on the top surface of the base 211 at intervals of a predetermined distance. The X-direction actuator 213 is constituted by a plurality of coil parts 215 and a plurality of air bearings 224.
By applying the current to the coil parts 215, the driving force is generated to move the movable stage part 217. The Y-direction actuators 214 are constituted by the plurality of coil parts 215 and the pair of air bearings 224. By applying the current to the coil parts 215, the driving force is generated in the X-direction actuator 213 and the Y-direction actuator 214, and the movable stage part 217 is moved.
The tilt actuator 216 is provided for adjusting the horizontal attitude of the movable stage part 217. The fixed stage part 219 is arranged integrally with the movable stage part 217. On the fixed stage part 219, the chuck 221 for mounting the work piece (the movable body) is arranged integrally with the fixed stage part 219.
The mirror 222 is arranged on the movable stage part 217. This mirror 222 is provided for reflecting the laser beam which is emitted by the light source. The laser beam is reflected to a laser measuring instrument 223 by the mirror 222, so that the position of the movable stage part 217 is measured by the laser measuring instrument 223.
In this position measuring device that determines the position in the X-Y direction using the laser interference displacement gauge 223, two displacement gauges are combined with a highly precise straightedge which covers the movement range perpendicular to the displacement measuring direction and has the guaranteed shape accuracy, and thereby performing the position detection.
Among other conventional position measuring devices, there are known position measuring devices which have the structure in which a given number of measuring devices, such as rotary encoders and linear encoders, are arranged for a given number of degrees of freedom. For example, when performing two-dimensional positioning, one of the position measuring devices having such structure may be configured so that the stage which is moved in the X-direction and the stage which is moved in the Y-direction are accumulated independently of each other. Another of the position measuring device having such structure may be configured so that the peripheral scale and the one-axial stage are combined, and a rotational position and a radial position are measured independently, and positioning is performed.
Conventionally, when detecting the position equivalent to pitching and yawing angles of a moving body, the autocollimator has been used. This autocollimator is adapted to measure the pitching and yawing angles of the moving body simultaneously with respect to movement in the straight line direction along one axis, but it requires the highly precise straightedge to measure the position of the moving body in the X-Y direction thereof.
Moreover, the level vial is known as the device which measures the rolling angle of a moving body. However, the level vial has a problem in the response speed and measurement accuracy, and it is unsuitable for a high accuracy measuring device.
To obviate the problem, the method in which two parallel straightedges are arranged to compute a rolling angle from a difference between the distances to the straightedges has been used. Moreover, the method in which a single straightedge is arranged as a reference mirror surface to detect a rolling angle using an autocollimator has been used. See Japanese Laid-Open Patent Application No. 05-328702.
However, the following problems arise in the stage device using the above-mentioned conventional position measuring device. That is, the measuring device used in the conventional position measuring device, such as a rotary encoder or a linear encoder, can perform only one-dimensional positioning. In order to perform two-dimensional positioning, it is necessary to combine at least two sets of the above-mentioned measuring devices. And the design of a moving body position measuring device has a considerable constraint in the structure thereof.
Also in the case in which positioning is performed using the laser measuring instrument 223, what can be performed is only one-dimensional positioning. In order to perform two-dimensional positioning, it is necessary to use the straightedge which is constructed with high accuracy. Consequently, when the position measuring device of this kind is provided in the stage device, there is a constraint in the structure thereof, and the manufacturing cost becomes high.